(Physiology) - Genes Flashcards
Gregor Mendel
character and trait
LOCUS AND GENERATIONS
his experiment
his hypothesis
studied inheritance using pea plants
purple leafs always produced purple
White one always produced white
mix the two, get purple or white
basic laws of heredity
In P generation mix white and purple
in F1 only purple
in F2 3 purple one white
3:1 RATIO
Character: a heritable feature, such as eye colour or hair colour
Trait: a variant of a character, such as blue eyes or brown eyes
- There are alternative versions of genes called alleles
- An organism inherits two alleles, one from each parent
- If the two alleles at a locus differ
The dominant allele determines appearance
The recessive allele has no noticeable effect on appearance - The law of segregation
The two alleles for a heritable character separate during gamete formation and end up in different gametes
How with reference to the flowers, will white show up in F2 generation
punnet square
purple is mixed with white and purple is dominant so purple is seen
each one has gametes
this produces the F1 generation and have a combo of Pp
half receive the big P and half receive the little p
in F2 generation Pp is breeded with Pp
each square is equally probable
shows the 3:1 ratio Mendel observed
Phenotype and genotype for flowers
allele arrangements
Homozygous- Same genes, Either dominant or recessive
Heterozygous- Differing genes, Dominant trait is
displayed
PP
Pp
Pp
pp
some traits determined by allele pairs
Ear lobe shape
Taste sensations
Rolling tongue
freckles
What do Punnett Squares show?
what are the outcome if TTxTT, TTXTt, TtxTt
or ttxTT or ttxtt
RECESSIVE DISORDERS- how the genotype and phenotype words, must they be homo or hetero
Probability of getting of inheriting a trait, compare allele from parents
DOMINANT TRAIT
TT x TT - 100% with trait
TTxTt - 100% with trait, 50% heterozygous GENOTYPE
TTxtt - 100% with trait, 100% heterozygous GENOTYPE
Tt and Tt- 75% will have the trait
25% will not have the dominant trait
50% heterozygous GENOTYPE
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Most disorders are recessive
Show up only in individuals
HOMOZYGOUS for the allele
25% chance to have deaf child
heterozygous individuals CAN carry the recessive allele but are phenotypically normal
Pedigree
follow family tree and relationships, follow traits thru genetic lines
Inheritance patterns of DOMINANT OR RECESSIVE traits can be traced
examples of recessive disorders
CiST GP
Cystic Fibrosis
Sickle Cell Anemia
Tay-Sach’s Disease
Gaucher’s Disease
Phenylketonuria
Dominant genetic disorders
are they seen in homo or hetero
examples
seen in heterozygous and homozygous dominant people
as long as they carry the dominant gene
Huntington’s disease
* Neurodegenerative
* effects seen after age 40
Marfan’s syndrome
* Affects connective tissue
- long limbs
- concave chest
Codominance
&
Incomplete Dominance
Two dominant alleles each distinctly affect the phenotype
More than 2 allele forms
E.g. Human blood
groups, Both A and B phenotypes
are dominant, O is recessive
types: a, b, ab, o
————————————————–
Phenotype of F1 offspring is between the phenotypes of the two parental varieties
Human example
Eye/hair/skin colour?
* Heterozygous people can
show mild symptoms of SICKLE CELL
Pleiotrophy
example in humans
where one gene has multiple phenotypic affects
sickle cell
one amino acid has gone wrong, protein can’t fold properly and therefore can’t hold OXYGEN right
breakdown and clumping and clumping of RBCs
Polygeny
Polygeny
When traits are determined by two or more genes
CONTINUUM
Skin color, hair colour
Vary along a continuum called quantitative characters
Sex linked traits punnett square
HEMOPHILIA
little h is hemophilia
If mother is heterozygous for a recessive X-linked trait
50% of the daughters will be carriers
50% of sons will show recessive trait
NO ALLELE ON Y
sex linked genes
sex linked traits
males can be hemizygous dominant or recessive, on the X gene,
like hemophilia if males have it they will show it because we only have one X
if recessive they wont
for females Homo dominant or recessive or Hetero
Sex linked disorders
Most are recessive, Affect males more because they only have one X
Has a single X-linked allele from his mother
Will have disorder if has allele
A female
Has two X alleles
* Needs recessive allele from both parents for disease
* If only one allele- carrier
Sex linked trait
Colour-Blindedness
9 % of males / 0.03% of females
because it is a recessive on X chromosome
Hemophilia
Male pattern Baldness
Gene expression
envn factors
Having a gene doesn’t mean it’s expressed
Epigenetic effects- on top of genetic affects
Histones and methylation
histones can deactivate or activate genes or their expression
Environmental factors determine epigenetics
- Alcohol, smoking, stress, diet, sleep
Cancer genes
is the cancer gene expressing?
Human disease
Lifestyle choices matter
Genetics may increase risk but lifestyle and envn is a huge factor
Eg. Heart disease and cancer
